Organ stop control



May 26, 1953 F. M. SCHMIDT ORGAN STOP CONTROL Filed Nov.I 1, 1947 ILT INVENToR.

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l QI l @n g r, j L lln' Patented May 26, 1953 ORGAN STOP CONTROL Francis M. Schmidt, North Tonawanda, N. Y., assignor to The Rudolph Wurlitzer Company, North Tonawanda, N. Y., a corporation of Ohio Application. November 1, 1947, Serial No. 783,512

(Cl. SI1- 1.13)

10 Claims.

This invention relates to electric organs, particularly or the type wherein a single key or pedal may serve to actuate or energize a plurality oi tone generators which are selectively rendered eiective in accordance with the desired stop or stops that are to be played.

ln the copending application of Victor I. Zuok, Serial No. 719,696, led January 2, 1947, Patent No. 2,570,178, issued October 2, 1951, there is disclosed an electric organ of the aforesaid type in which tone generators, such as vibrating reeds, are arranged in a plurality of sets respectively corresponding to the organ stops, and are actuated in tone groups among the several sets by operation of the organ keys. It is necessary to provide a switching means whereby only those tone generators which are in sets corresponding to the selected organ stops can furnish an audible output.

An object ol the present invention is to provide an improved stop control to perform the switching function just described.

A further object is to provide an electronic stop control of novel design such that operation of a stop switch does not produce any abrupt changes in volume of the reproduced tones.

A still further object is to provide an electronic stop control of such character that opening and closing oi the stop switches does not produce unpleasant eiects in the music.

Still another object is to provide an improved electric organ having the foregoing ieatures and in which each stop switch is arranged to control the bias oi an amplier tube in a preamplifier associated with the particular set of reeds pertaining to the selected stop.

'Ille above and other features and advantages of the invention will be apparent from a study of the specification and the accompanying drawing wherein:

Fig. l is a side elevation of an electric organ adapted to utilize my present invention;

Fig. 2 is a block diagram of an electric organ embodying my invention; and

Fig. 3 is a schematic circuit diagram of a preamplifier adapted to function as part of a stop control in accordance with the principles of the invention.

Referring to Fig. 1, the organ set forth for illustrative purposes is a single-manual instrument of the vibrating-reed type having a keyboard a set of stop tablets 8 disposed above the keyboard, a windchest I@ located behind the keyboard 6, a tone generating unit I2 comprising a plurality of vibrating-reed capacitors, an

air compresser I4 communicating with the windchest Ill, and an amplifying section I6.

The vibrating-reed capacitors (which may be referred to simply as reeds) in the tone generating unit I2 are arranged in banks or sets as indicated in Fig. 2. Thus, there are provided a bank of reeds I8 designated flute a second bank of reeds 2li designated viole and a third bank of reeds 22 designated diapason For sirnplicity, it will be assumed that each bank of reeds corresponds to a similarly designated organ stop, although in practice the reeds in each bank may produce the tones for a number of stops. Also, there may be combination stops, or several sets of pickups from the same tone generators, but for the purpose of explaining the present invention as expeditiously as possible such arrangements Awill not be considered.

The keys 24 in the keyboard 6 control air valves or pallets (not shown) between the wndchest Ill and the tone generating unit I2. The various keys 24 and the reeds I8, 2li and 22 in the several sets thereof are designated in Fig. 2 according to the tones of the chromatic scale. Each key 24 controls the admission of air from the windchest IE) to all of the reeds pertaining to that particular tone. For example, if the key 24 pertaining to the tone A in a given octave is actuated. it causes all of the reeds I8, 2D and 22 capable of producing that tone A to be set in vibration. Such an arrangement greatly reduces the number of pallets and pallet operating mechanisms required in an organ.

The stop tablets 8, of which only three are shown in Fig. 2, respectively control the operation of the preampliers 26, 28 and 3l] respectively associated with the banks of reeds I8, 20 and 22. A common electrical output conductor leads from the reeds of each bank (that is to say, of each organ stop) to an input of the related preamplier. Actuation of a particular stop tablet 8 renders the associated preamplier 2B, 28 or 30 effective to pass signals from the associated reed bank to a nal amplifier 32 which feeds the loudspeaker or loudspeakers 34, the manner in which this is accomplished being explained presently. The various preampliiiers as 26, 28 and 30 and the amplifier 32 together constitute the amplifying section I6, Fig. l.

In Fig. 3 there is illustrated a preamplifier unit of the type contemplated herein. Direct-current polarizing voltage is impressed upon one of the plates of each reed capacitor in the bank such as I8. The other plates of the capacitors are connected through a common conductor 36 to the grid input terminal of a tube 38 in the first stage of the preamplier as 26. The output of tube 38 is coupled in a conventional manner to the input of a tube 40 in the second stage of the preamplier. The output of tube 4!! is delivered to a voltage divider comprising the series-connected resistors 42 and 411. IThe output voltage of the preamplifier is taken across the load resistor 44 Each stop tablet il is arranged to actuate a switch as 46, Fig. 3. One terminal of the switch 46 is grounded while the other terminal is connected through a resistor 48 to the cathode 5U of the ampliiier tube 40, this cathode being connected to ground through a biasing resistor 52. A capacitor 5:1 is connected in shunt with the resistor 52. The resistors 43 and 52 are included in a voltage divider which also includes a resistor 5G connected to the source of plate voltage. A capacitor 58 is connected between ground and the junction of the resistors t3 and 5E, thus being connected also across the contacts of the switch 45.

The opera-tion o the illustrated apparatus will be described insofar as it concerns the flute bank of reeds i8 and the preamplifier 26, it being understood that the operation is similar insofar as other reed banks and preampliiiers are concerned. When the switch 4S, Fig. 3, controlled by the stop tablet 8 is open, current flows from the source of plate voltage through the voltage divider network comprising resistors 5B, 48 and 52 to ground. The voltage drop across the resistor 52 under these conditions maintains the potential of the cathode lill sufficiently high to render :Y

the tube 4t inoperative. Hence, no signals Will be passed from the bank of reeds I8 to the arnpliiier 32, Fig. 2. When the stop tablet 8 is depressed to close the switch 45, however, the

resistor 48 is connected in parallel with the re- .1

sistor 52 and the capacitor 55 between the cathode 50 and ground. rl'he elements just mentioned comprise a timingr circuit which permits the voltage on the cathode EG gradually to diminish over a predetermined time interval to a level where the tube 49 is rendered effective to amplify and pass signals from the reed bank I8. The tube 4D then operates as a normal self-biased ampliiier.

The timing arrangement described insures that there will be no abrupt change in sound produced by the organ as an incident to closing a stop switch such as 45. The volume of the reproduced sounds originating in the bank of reeds i8. for example. is built up in a smooth, natural manner to produce a pleasing effect upon the listener. Obviously the rate at which the timing circuit functions may be varied by changing the values of the circuit parameters.

llfhen the stop switch Fig. 3, is opened, the resistor` 53 and capacitor act as a timing circuit causing the potential of the cathode 50 to rise gradually toward its normal high level at which the tube fl@ ceases to function. Thus, opening of the switch does not cause an abrupt cessation of the reproduced sounds originating in the bank of reeds IIJ. Instead, the volume of such sounds gradually is reduced over a predetermined time interval depending upon the values of the circuit parameters.

It should be noted that both of the above described timing circuits have some effect on the response of the preamplier when the switch 4G is opened or when it is closed. However, the timing circuit including resistor 48 and capacitor 54 is primarily effective when the switch 46 is closed, while the timing circuit comprising the resistor 55 and capacitor 58 is primarily effective when the switch 4S is opened. Practical design considerations may require that these timing circuits operate fairly rapidly, but it is possible to avoid any undesirable effects as a result of such rapid action by properly proportioning the resistors 42 and M in the output circuit of the tube 40.

From the foregoing description it is apparent that I have provided an electronic stop control for organs which fuliills the above stated purposes of the invention. This stop control will be found particularly useful in situations where several banks of reeds are actuated simultaneously and a selection to be made of the reed banks which are to be eiective in furnishing the output of the organ. However, it should be understood that the invention is not necessarily limited to such applications, as it may have utility in other types ol organs as well.

Various changes may be made in the specific embodiment seiv forth for purposes of illustration Without departing from the spirit of the invention. and it is intended that such modifications as may readily occur to persone skilled in the art shall be included in the scope of the ioliowing claims.

The invention is hereby claimed as follows:

li In an electric organ of the type wherein a plurality of tone generators related to various stops is adapted to be operated simultaneously by a single key, a pluralityv of tone generators a1'- ranged in sets, a plurality of electronic amplifying devices each having an input, means for rendering said amplifying devices inoperative, means for connecting each input to only one set of tone generators to control the passage of signals from a set of a plurality of tone generators pertaining to a given organ stop, biasing potential means, a plurality of organ stop switches, means interconnecting each electronic amplifying device with one switch, means interconnecting each switch with said biasing potential means for respectively a-nd independently applying said bias to one of said amplifying devices to render said respective amplifying device operative.

An electric as claimed in claim 1, having timing means interconnected with each electronic amplifying device to the response of each electronic amplifying device to operation of its related switch.

3. An electric organ as claimed in cla-im 2, wherein said timing means comprises `at least one resistance-capacitance timing circuit.

4. An electric organ as claimed in claim l, wherein said means for rendering said amplifying devices inoperative a source' of cut-off potential rendered ineffective by operation of said switch.

5. An electric organ as claimed in claim 4, wherein the switch means associated with each amplifying device has one position in which said source of cut-off potential is applied to said amplifying device to render said device non-conductive, and another position in which said cutoff potential is removed from said amplifying device and said biasing potential means is connected to said amplifying device to render said device conductive.

6. An electric organ as claimed in claim 5, wherein a resistance-capacitance timing means is in circuit with said source of cut-off potential when said switch means is in said one position, said timing means delaying the response of said amplifying device when said switch is moved to said other position.

7. An electric organ as claimed in claim 5, having a timing means to delay the response of said amplifying device to movement of said switch to said one position, said timing means comprising a capacitance and a resistance in series with said capacitance and said source of cut-01T potential, said 4capacitance being shunted by said switch when said switch is in said other position.

8. An electric organ as claimed in claim 1, wherein a source of cut-off potential is connected to each respective amplifying device by a separate voltage divider, each of said voltage dividers including a plurality of resistance elements, the switch means associated with each respective amplifying device having one position in which all of said resistance elements are connected in series with each other to thereby apply said cutoff potential to said amplifier, said switch means having another position in which at least two resistance elements of said voltage divider are placed in parallel to render effective said biasing potential means and render ineffective said cutoff potential.

9, An electric organ as claimed in claim 1, wherein said biasing potential means comprises a cathode bias resistance element connected in the cathode circuit by operation of said switch.

10. An electric organ as dened in claim 1, wherein a source of cut-01T potential is connected to each respective amplifying device by a separate voltage divider, one end of said voltage divider being connected to ground, the other end of said voltage divider being connected to a point which is positive with respect to ground, each respective amplifying device having a cathode connected to said voltage divider intermediate the ends thereof to normally render said amplifying device inoperative, said switch means having one side connected to said voltage divider intermediate said cathode connection and said positive point, the other side of said switch means being connected to ground, closure of said switch means being effective to render said amplifying device operative.

FRANCIS M. SCHMIDT.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,877,317 Hitchcock Sept. 13, 1932 2,126,682 Hammond Aug. 9, 1938 2,173,888 Smiley Sept. 26, 1939 2,354,699 Owens Aug. 1, 1944 2,432,152 Hanert et al Dec. 9, 1947 

